BBOTs unarchive module rejects archives containing symlink entries before extraction, but for zip and 7z archives it failed to detect symlinks whose listing carries a DOS-attribute prefix before the unix mode, as produced by legacy versions of p7zip. Such an archive, downloaded and extracted during a scan (for example via filedownload), bypassed the guard and caused an attacker-controlled symlink to be written into the extraction directory. The effect is limited to planting the symlink (its target is not written through), and only hosts using such a legacy p7zip build are affected; current mainline 7-Zip is not.
Weakness
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
Potential Mitigations
- Follow the principle of least privilege when assigning access rights to entities in a software system.
- Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/132.html
- https://cwe.mitre.org/data/definitions/17.html
- https://cwe.mitre.org/data/definitions/35.html
- https://cwe.mitre.org/data/definitions/76.html